RTLS systems estimate locations for moving tags within a floor plan of interior rooms, in buildings such as hospitals. Many RTLS systems based on radio-frequency signals such as BLE, are designed to have moving tags that transmit a BLE advertisement, in a field of receiving devices called BLE gateways, sensors, bridges or Access Points. A network of BLE gateways will use received signal strength of advertisements from a tag, as a proxy for estimating the distance between the tag and each gateway and use multi-lateration algorithms to estimate the locations of tags. Those approaches with tags that transmit are standard in the industry and provide location estimates that are acceptable for may use cases in industrial and manufacturing environments. But they fail to scale to provide an efficient location system for the largest environments with a dense deployment of tags, like large hospitals.
To illustrate the scaling problem, imagine a hospital with 10,000 tags, each of which are beaconing 3 times per second, within a field of BLE gateways that report received signal strength to a location engine. Perhaps 1000 of those tags move each hour to a new location. At least three BLE gateways MUST hear a tag to be tri-laterated. In practice, systems are typically designed so that as many as five-to-ten gateways hear each tag, for redundancy in case some gateways are blocked or do not successfully hear the tag. In addition, gateways on floors above and below the tag may hear the tag transmission and must forward the signal-strength readings. So for demonstration of the limitations on scaling of the standard industry design, let's assume that ten gateways hear each tag transmission and forward the reading to the location engine. Ten-thousand (10,000) tags transmitting 3 times per second create 30,000 beacons transmitted per second. If ten gateways hear each ping and forward those messages to the location engine, the location engine receives 300,000 signal-strength readings per second. That extrapolates to about 1 billion readings received per hour, which must all be processed to determine the locations of tags. Even though only a fraction of the 10,000 assets would have moved in that hour, a billion messages would be processed to discover which tags had moved, and the new locations of the assets which may have moved. Forwarding and processing those billion messages per hour requires substantial networking and computing resources. Thus, new solutions using fewer resources are needed to better locate and track large numbers of assets.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.